Network protocols are the rules by which systems talk. Application protocols (HTTP, SMTP, FTP, SSH) ride on transport (TCP, UDP, QUIC) and are the bread and butter of enterprise integration.
3.4 Network Protocols and Web Services
Application protocols
Protocol
Layer
Use
HTTP / HTTPS
App
Web, REST APIs
HTTP/2, HTTP/3
App
Modern; multiplexed; QUIC for /3
WebSocket
App
Persistent bidirectional
SMTP / IMAP
App
Mail send / receive
FTP / SFTP
App
File transfer (SFTP preferred)
SSH
App
Remote shell + tunnels
LDAP / LDAPS
App
Directory queries (AD)
RDP
App
Remote desktop
RTP / SRTP
App
Real-time audio + video
Web services - four flavours
Style
Format
When
SOAP
XML envelopes
Legacy enterprises; strong contracts
REST
HTTP verbs + JSON
De-facto default
GraphQL
Single endpoint
Client-shaped queries
gRPC
HTTP/2 + protobuf
High-performance polyglot
REST resource design (Sample Bakery Shop)
Verb
URL
Action
GET
/orders
list orders
POST
/orders
create order
GET
/orders/{id}
read one
PATCH
/orders/{id}
update fields
DELETE
/orders/{id}
cancel order
GET
/orders/{id}/items
nested resource
HTTP status codes - the ones to remember
Code
Meaning
Code
Meaning
200
OK
400
Bad Request
201
Created
401
Unauthorised
202
Accepted
403
Forbidden
204
No Content
404
Not Found
301
Moved Permanently
409
Conflict
304
Not Modified
422
Unprocessable Entity
500
Server Error
429
Too Many Requests
502
Bad Gateway
503
Service Unavailable
Authentication patterns
Pattern
Use
Basic
Username:password; HTTPS-only
Bearer (JWT)
Signed token in Authorization header
OAuth 2.0
Delegated authorisation; cloud apps
mTLS
Both ends present certificates
Mentor’s tip: HTTP and HTTPS are the universal transport. REST + JSON is the common dialect; SOAP, GraphQL, gRPC are domain-specific tools. Standardise on one auth pattern across the enterprise.
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